CVE-2026-56392: GNU coreutils unexpand is vulnerable to a heap-based buffer overflow due to an integer overflow during buffer

Routine

MEDIUM 6.1MITIGATE

CVE-2026-56392 is a medium-severity flaw (CVSS 6.1) affecting coreutils. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

GNU coreutils unexpand is vulnerable to a heap-based buffer overflow due to an integer overflow during buffer allocation when processing large tab stop (-t) values. The multiplication used to calculate the allocation size can wrap around, resulting in an undersized buffer. When processing crafted input, subsequent writes exceed the allocated memory, leading to an out‑of‑bounds heap write. When running GNU coreutils unexpand with attacker-provide

Why this priority

No elevated risk signals yet

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 92%)
CISA exploited list	No
Weakness	CWE-122
Published	2026-07-24
Last modified	2026-10-24

Publisher (CNA): CERT.PL · Vendor: gnu

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-24 09:16 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

gnu coreutils MITIGATE

Affected: 9.11

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy coreutils || rpm -q coreutils || coreutils --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Downgrade not recommended

This is a core system component: downgrading can break the OS. Apply the distro update or the vendor mitigation.

Advisories and coverage

Official advisories

CERT Polska: Vulnerabilities in GNU coreutils software 2026-07-24

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-56392?

coreutils: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-56392 being exploited?

CVE-2026-56392 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-56392 affect?

CVE-2026-56392 affects coreutils. Severity is medium (CVSS 6.1). GNU coreutils unexpand is vulnerable to a heap-based buffer overflow due to an integer overflow during buffer allocation when processing large tab stop (-t) values. The multiplication used to calculate the allocation size can wrap around, r

How urgent is CVE-2026-56392?

Priority 23/100. No elevated risk signals yet.

Related CVEs

CVE-2026-56391 MEDIUM 6.1 UPGRADE GNU coreutils uniq is vulnerable to an out‑of‑bounds read due to incorrect handling of multibyte input when th

References

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